1. Field of the Invention
This invention relates to a combustor that is preferably used to reduce an amount of NOx exhaust and the combustion oscillation, and to a gas turbine and a jet engine which are equipped with the combustor.
2. Description of Related Art
Reduction of Nox emissions is required, in view of recent environmental problems, when a gas turbine and a jet engine are used.
A gas turbine and a jet engine each include a compressor, a combustor, and a turbine. The compressor and the turbine are connected to each other by means of a main shaft. The combustor is connected to an outlet of the compressor.
A working fluid gas is compressed by the compressor in order to supply a high-pressure gas to the combustor. The high-pressure gas is heated to a predetermined turbine inlet temperature by the combustor in order to supply a high-pressure and high-temperature gas to the turbine. The high-temperature and high-pressure gas is expanded in a cylinder of the turbine, as the high-temperature and high-pressure gas passes between a stator blade and a rotor blade disposed on the main shaft of the turbine. The main shaft is thereby rotated that a shaft output is generated. In a gas turbine of this type, a shaft output can be obtained by subtracting the power consumed for rotating the compressor. Therefore, the shaft output can be used as a driving source by connecting an electric power generator to the main shaft at the opposite side of the turbine, for example.
The jet engine uses the output in the form of the kinetic energy of a high-velocity jet to directly propel an aircraft.
The development of the gas turbine and the jet engine described above has been promoted in order to reduce emissions of NOx and the like in view of recent environmental problems. In a premixing combustion mode, fuel gas and air are premixed. When the fuel gas is non-uniformly premixed, a high concentration area of the fuel gas is generated. At the high concentration area, a flame is generated which has a temperature that is locally highly elevated, At the high temperature portion of the flame, a large amount of NOx is emitted, so that the total amount of NOx exhaust is increased. Therefore, it is effective to make uniform the mixed ratio of the fuel gas and the air, in order to reduce the amount of NOx exhaust.
A gas turbine combustor which can premix the fuel gas and the air at a subsequently equal ratio is disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 11-141878, for example. The gas turbine combustor is provided with a straightening plate, which has a plurality of small through holes, on the air intake side of the main body of the gas turbine combustor. The straightening plate makes the air, which is supplied to the gas turbine combustor, flow uniformly. Thereby, the fuel gas and the air can be premixed uniformly.
In the following, the gas turbine combustor will be briefly explained with reference to FIGS. 19 and 20. In FIG. 19, a combustor 1, an internal cylinder 2, a premixing nozzle 3, a pilot burner 4, a main burner 5, and a top hat 6 are shown. The premixing nozzle 3 includes the pilot burner 4 and the main burner 5. An air flow passage 7 is formed between the internal cylinder 2 and the top hat 6. In the air flow passage 7, air is supplied from the compressor.
The direction of the air flow is shown by arrows in FIG. 19. That is, the air flow supplied from the compressor is reversed to be supplied to an inlet of the air flow passage 7. Then, the air flow supplied from an outlet of the air flow passage 7 is reversed to be supplied to the combustor 1. Near the outlet of the air flow passage 7, a straightening plate 8 having a plurality of small through holes 8a is provided so as to cover the outlet of the air flow passage 7. The air flow passing through the straightening plate 8 is made uniform, and is supplied to the tip end positions of the pilot burner 4 and respective main burners 5. Therefore, the fuel gas and the air are uniformly premixed so that the amount of NOx exhaust can be reduced.
By using the gas turbine combustor, the premixed gas is ignited to form a flame which burns in a thin narrow area and in a short time. Thereby, the calorific value generated per unit area is increased in the gas turbine combustor. By the increase of the calorific value, combustion oscillation is generated. When the combustion oscillation is generated, the combustion oscillation is propagated as pressure waves, and resonates as an acoustic system consisting of casings of the combustor, the gas turbine, and the like. Therefore, there is a danger of internal pressure fluctuation as the combustion oscillation is enlarged. In this case, it is difficult to operate normally the gas turbine combustor and the like.
Moreover, in the gas turbine combustor, the turbulence of the air flow supplied from the compressor tends to be increased, and to be maintained for a long time. Thereby, the turbulence during the combustion is so strong that the combustion tends to be unstable. When combustion is unstable, combustion oscillation is generated. The combustion oscillation causes internal pressure fluctuation in the combustor. Then the pressure waves caused by the internal pressure fluctuation are propagated and resonate with the acoustic system consisting of the casings of the combustor, the gas turbine, and the like. Thereby, the internal pressure fluctuation causing the combustion oscillation may be enlarged. Therefore it becomes difficult to operate normally the gas turbine combustor.
The present invention has been made to solve the problems described above. An object of the present invention is to provide a combustor, which can reduce the amount of NOx exhaust and the combustion oscillation at the same time, and is provided with a gas turbine and a jet engine.
In order to achieve the object described above, the present invention utilizes the following constitution.
A combustor according to the present invention includes a combustion unit, an air flow passage through which air is supplied to the combustion unit from a compressor, and a velocity fluctuation absorption member which is provided in the air flow passage near the maximum velocity fluctuation position in the air flow passage where the velocity fluctuation of the air flow becomes maximum.
A combustor according to the present invention includes a premixing nozzle, a first cylindrical member which accommodates the premixing nozzle, a second cylindrical member which accommodates the first cylindrical member, and an air flow passage through which air is supplied from a compressor to the premixing nozzle and is accommodated in the second cylindrical member, and a velocity fluctuation absorption member which is provided in the air flow passage near the maximum velocity fluctuation position in the air flow passage where the velocity fluctuation of the air flow becomes maximum.
In these combustors, the velocity fluctuation absorption member may be disposed in the vicinity of the maximum velocity fluctuation position in the air flow passage in the range of xc2x1xe2x85x9xcex, wherein xcex is a wavelength of the velocity fluctuation.
The velocity fluctuation absorption member may be disposed at an inlet of the air flow passage.
When the combustors described above are used, the air flow is supplied from the compressor to the combustion unit (the premixing nozzle) through the velocity fluctuation absorption member disposed near the maximum velocity fluctuation position in the air flow passage where the velocity fluctuation of the air flow becomes maximum. The velocity fluctuation absorption member provides resistance to the pressure waves of the combustion oscillation and to the turbulence of the air flow supplied from the compressor. Thereby, the pressure fluctuation is increased at the maximum velocity fluctuation position, and the difference between the velocity fluctuation and the pressure fluctuation is decreased. Thus, the pressure waves of the combustion oscillation and the turbulence of the air flow can be reduced. The velocity fluctuation absorption member also works as an acoustic damper which reduces the internal pressure fluctuation. The resonation of the combustion oscillation and the acoustic system can thereby be prevented, and increase of the combustion oscillation can also be prevented. The velocity fluctuation absorption member makes the air flow uniformly in the air flow passage, so that the velocity of the air flow is made uniform and the turbulence of the air flow is reduced. The amount of NOx exhaust can thereby be reduced. Thus the reduction of the NOx emissions and the combustion oscillation can be reduced at the same time and stable operation of the combustor can be achieved.
In the combustor, the velocity fluctuation absorption member used may be a punched metal plate, a net member, or a porous plate, which can cause a pressure loss of the air flow. Preferably, an aperture ratio of the velocity fluctuation absorption member may be no less than 35% with respect to the cross-sectional area of the velocity fluctuation absorption member in which apertures are formed, so that highly effective operation of the combustor is maintained.
In the combustor, the air flow passage may be provided with a straightening member for the air flow so that the air flow is made uniform and the axial velocity of the air flow is made uniform. The concentration distribution of the premixed gas is thereby made uniform so that the amount of NOx exhaust is reduced.
In the combustor, the premixing nozzle preferably includes a fuel discharge member which is fixed on a fuel supply conduit and includes a main body having an internal space which communicates with a fuel passage in the fuel supply conduit, fuel discharge outlets which communicate with the internal space and a trailing edge having a thickness of no more than 5 mm, or a flow passage block ratio of the fuel discharge member that is no more than 10% with respect to the cross-sectional area of the air flow passage in which the fuel discharge member is to be placed. By using the combustor, the generation of swirl downstream of the fuel discharge member is reduced, so that the concentration distribution of the premixed gas is made uniform.
In the combustor, the premixing nozzle preferably includes the fuel discharge member which is fixed on the fuel supply conduit and includes the main body having an internal space which communicates with the fuel passage in the fuel supply conduit, the fuel discharge outlets which communicate with the internal space, and the trailing edge, wherein the main body is a flat tube. By using the combustor, the generation of swirl downstream of the fuel discharge member is reduced, so that the concentration distribution of the premixed gas is made uniform.
A gas turbine according to the present invention includes a compressor which compresses air to generate a high-pressure gas, the combustor described above, which is connected to the compressor so as to be supplied with the high-pressure gas from the compressor, and which heats the high-pressure gas to generate a high-temperature and high-pressure gas, and a turbine which is connected to the combustor so as to be supplied with the high-temperature and high-pressure gas from the combustor, and which rotates an output shaft by expanding the high-temperature and high-pressure gas to generate a shaft output.
When the gas turbine is used, which includes the combustor provided with the velocity fluctuation absorption member, the velocity fluctuation absorption member provides the resistance to the pressure waves of the combustion oscillation and to the turbulence of the air flow supplied from the compressor. The pressure fluctuation is thereby increased at the maximum velocity fluctuation position, and the difference between the velocity fluctuation and the pressure fluctuation is decreased. The pressure waves of the combustion oscillation and the turbulence of the air flow can thereby be reduced. The velocity fluctuation absorption member also works as an acoustic damper which reduces the internal pressure fluctuation. The resonation of the combustion oscillation and the acoustic system can thereby be prevented, and increase of the combustion oscillation can be prevented. The velocity fluctuation absorption member wakes the air flow uniform, so that the velocity of the air flow is made uniform and the turbulence of the air flow is reduced. Thereby, the amount of NOx exhaust can be reduced. Thus, the reduction of the NOx emission and the combustion can be reduced at the same time, and the stable operation of the combustor can be achieved.
A jet engine according to the present invention includes a compressor which compresses air to generate a high-pressure gas, the combustor described above, which is connected to the compressor so as to be supplied with the high-pressure gas from the compressor, and which heats high-pressure gas to generate a high-temperature and high-pressure gas, and a turbine which is connected to the combustor so as to be supplied with the high-temperature and high-pressure gas from the combustor.
When the jet engine is used, which includes the combustor provided with the velocity fluctuation absorption member, the velocity fluctuation absorption member provides the resistance to the pressure waves of the combustion oscillation and the turbulence of the air flow supplied from the compressor. The pressure fluctuation is thereby increased at the maximum velocity fluctuation position, and the difference between the velocity fluctuation and the pressure fluctuation is decreased. The pressure waves of the combustion oscillation and the turbulence of the air flow can thereby be reduced. The velocity fluctuation absorption member also works as an acoustic damper which reduces the internal pressure fluctuation. The resonation of the combustion oscillation and the acoustic system can thereby be prevented, and the increase of the combustion oscillation can be prevented. The velocity fluctuation absorption member makes the air flow uniform, so that the velocity of the air flow is made uniform and the turbulence of the air flow is reduced. Thereby, the amount of NOx exhaust can be reduced. Thus, the reduction of the NOx emissions and the combustion oscillation can be reduced at the same time, and stable operation of the combustor can be achieved.